Hartvig Christie1
1Norwegian Institute for Water Research, Norway
Zooming into a site in Lofoten, northern Norway, we can follow several shifts in ecosystem states from the1970ies and until today. Zooming out, we can explore how representative the different ecosystem states are in a regional or national perspective. The shifts over time have been: transformation of pristine kelp forests to green sea urchin (Strongylocentrotus sp.) barrens; from green sea urchin desert to a transition of Cancer crab predation on urchins; recovery of the kelp forests due to cancer crab removal of urchins; kelp forests being replaced by turf/filamentous algae; and a new sea urchin desert created by red sea urchin (Echinus esculentus) grazing. The shifts are induced by anthropogenic stressors such as overfishing, ocean warming, eutrophication, and organic overloading. In addition to the human stressors, biological processes like predation, competition, top-down and bottom-up interactions are important drivers. The different states represent large differences in ecosystem structure, function, biodiversity and services. The regime shifts indicate that the ecological states are reversible, hence that restoration actions can be carried out to recover the productive and diverse kelp forest. Our findings can be used to guide kelp restoration actions.
Biography
Hartvig Christie is a senior scientist (emeritus) at Norwegian Institute for Water Research. He has been working with blue forest ecology and kelp forest fauna and recovery since the 1980ies. Important research topics include basic understanding of kelp and seagrass ecosystem structure, function and organization processes, species interactions, and the impact of stressors like sea urchin grazing, eutrophication, ocean warming, as well as impact of restoration techniques.